Holy Cow! That main gear is messed up. I've done that once before on my HBK2, gear mesh was too loose, I hit idle-up and it just ground them down like yours. Gear mesh is pretty critical on all helis. Too tight, causes binding and overloading the motor, to loose and you end up with a toasted main gear. Soft start would help, but eventually with a loose mesh, you'll have premature wear and tear on the main.

Here's a picture of correct gear mesh.

Dave